Optical element and imaging apparatus

ABSTRACT

An optical element is disclosed. The optical element may include a container having a holding chamber, a polar or conductive first liquid filled in the holding chamber, a second liquid filled in the holding chamber and not mixing with the first liquid, first and second electrodes for applying an electric field to the first liquid, and voltage application means for applying voltage between the first electrode and the second electrode.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.11/726,360 filed on Mar. 21, 2007, which claims priority for JapaneseApplication No. JP 2006-088810 filed on Mar. 28, 2006, the disclosure ofwhich is incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an optical element and an imagingapparatus.

2. Description of the Related Art

An optical element has been proposed which changes the opticalcharacteristic of a polar or conductive liquid by changing theconductivity or the form of the liquid based on an electric capillaryphenomenon (electrowetting phenomenon) through the application of anelectric field to the liquid.

Liquid moving means has been proposed which moves a polar or conductiveliquid itself in a desired direction by applying an electric field tothe liquid (refer to JP-A-2004-336898 (Patent Document 1)).

The liquid moving means includes a first electrode in contact with aliquid (or liquid drop), multiple second electrodes provided to a liquidthrough an insulating layer and aligned in a predetermined direction andcontrol means for controlling each voltage to be applied between thefirst electrode and each of the second electrodes. In this case, theliquid on the insulating layer is moved in the predetermined directionby changing the position subject to the application of voltage in thesecond electrodes by the control means.

BRIEF SUMMARY OF THE INVENTION

An increase in speed of the movement of a liquid is demanded in order toimprove the response property of a shutter including the liquid movingmeans on the optical axis of a shooting optical system of an imagingapparatus, in which the liquid is moved in the direction orthogonal tothe optical axis.

However, the technology in the past has a limited increase in strengthof the electric field to be applied to a liquid, which also limits theincrease in speed of the movement of the liquid.

Accordingly, it is desirable to propose an optical element, which isadvantageous for improving the response property, and an imagingapparatus including the optical element.

According to an embodiment of the present invention, there is providedan optical element which may include a container having a holdingchamber, a polar or conductive first liquid filled in the holdingchamber, a second liquid filled in the holding chamber and not mixingwith the first liquid, first and second electrodes for applying anelectric field to the first liquid, and voltage application means forapplying voltage between the first electrode and the second electrode,wherein the change of the position subject to the voltage application bythe voltage application means to the first and second electrodes maymove the first liquid in the second liquid within the holding chamber,the holding chamber may have an adjustment chamber adjusting the amountof transmitted light based on the presence of the first liquid andmultiple lay-by chambers connecting to the adjustment chamber andallowing the accommodation of the first liquid laid by from theadjustment chamber, the adjustment chamber and the multiple lay-bychambers may have first and second end walls facing against each otherin the direction that the light passes through, the first electrode maybe provided on one end wall of the first and second end walls of theadjustment chamber and multiple lay-by chambers, and the secondelectrode may be provided on the other end wall of the first and secondend walls.

According to another embodiment of the invention, there is provided anoptical element which may include a container having a holding chamber,a polar or conductive first liquid filled in the holding chamber, asecond liquid filled in the holding chamber and not mixing with thefirst liquid, first and second electrodes for applying an electric fieldto the first liquid, and voltage application means for applying voltagebetween the first electrode and the second electrode, wherein the changeof the position subject to the voltage application by the voltageapplication means to the first and second electrodes may move the firstliquid in the second liquid within the holding chamber, the holdingchamber includes first and second end walls facing against each other inthe direction that light passes through, the first electrode may beprovided on one end wall of the first and second end walls, and thesecond electrode may be provided on the other end wall of the first andsecond end walls, the second electrode may include a central electrodemember and multiple surrounding electrode members around the centralelectrode member, and the first electrode may include a single electrodemember facing against the central electrode member and the multiplesurrounding electrode members.

According to another embodiment of the invention, there is provided animaging apparatus which may include a shooting optical system conductinga subject image, an imaging element on the optical axis of the shootingoptical system, and an optical element before the imaging element on theoptical axis, wherein the optical element has a container having aholding chamber, a polar or conductive first liquid filled in theholding chamber, a second liquid filled in the holding chamber and notmixing with the first liquid, first and second electrodes for applyingan electric field to the first liquid, and voltage application means forapplying voltage between the first electrode and the second electrode,the change of the position subject to the voltage application by thevoltage application means to the first and second electrodes may movethe first liquid in the second liquid within the holding chamber, theholding chamber may have an adjustment chamber for adjusting the amountof transmitted light based on the presence of the first liquid andmultiple lay-by chambers connecting to the adjustment chamber andallowing the accommodation of the first liquid laid by from theadjustment chamber, the adjustment chamber and the multiple lay-bychambers may have first and second end walls facing against each otherin the direction that the light passes through, and the first electrodemay be provided on one end wall of the first and second end walls of theadjustment chamber and multiple lay-by chambers, and the secondelectrode may be provided on the other end wall of the first and secondend walls.

According to another embodiment of the invention, there is provided animaging apparatus which may include a shooting optical system conductinga subject image, an imaging element on the optical axis of the shootingoptical system, and an optical element before the imaging element on theoptical axis, wherein the optical element has a container having aholding chamber, a polar or conductive first liquid filled in theholding chamber, a second liquid filled in the holding chamber and notmixing with the first liquid, first and second electrodes for applyingan electric field to the first liquid, and voltage application means forapplying voltage between the first electrode and the second electrode,the change of the position subject to the voltage application by thevoltage application means to the first and second electrodes may movethe first liquid in the second liquid within the holding chamber, theholding chamber may have first and second end walls facing against eachother in the direction that light passes through, the first electrodemay be provided on one end wall of the first and second end walls, andthe second electrode may be provided on the other end wall of the firstand second end walls, the second electrode may include a centralelectrode member and multiple surrounding electrode members around thecentral electrode member, and the first electrode may include a singleelectrode member facing against the central electrode member and themultiple surrounding electrode members.

According to the embodiments of the invention, the application ofvoltage to the first liquid by the multiple electrode members in theholding chamber may divide and move the first liquid. Thus, the mass andtravel of the first liquid can be reduced in comparison with the casethat the first liquid is entirely moved. Therefore, the speed ofmovement of the first liquid can be increased, which is advantageous forimprovement of the response property of an optical element.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a section diagram describing the principle of movement of aliquid, and FIG. 1B is a view on the arrows A in FIG. 1A;

FIG. 2A is a longitudinal section diagram showing a construction of anoptical element 10, and FIG. 2B is a view on the arrows A in FIG. 2A;

FIG. 3A is a section diagram taken by the line B-B in FIG. 2A, and FIG.3B is a view on the arrows C in FIG. 2A;

FIG. 4 is an explanatory diagram describing an operation of the opticalelement 10;

FIG. 5 is an explanatory diagram describing an operation of the opticalelement 10;

FIG. 6 is an explanatory diagram describing an operation of the opticalelement 10;

FIGS. 7A and 7B are explanatory diagrams describing an operation of theoptical element 10;

FIG. 8 is a block diagram showing a construction of an imaging apparatus100;

FIG. 9 is a diagram showing a construction of a shooting optical system104 of the imaging apparatus 100;

FIG. 10A is a diagram describing the movement of a first liquid 14 in acomparison example, and FIG. 10B is a diagram describing the movement ofthe first liquid 14 according to an embodiment;

FIGS. 11A and 11B are plan views showing a variation example of a secondelectrode 20;

FIG. 12 is a longitudinal section diagram showing a construction of theoptical element 10 according to a second embodiment;

FIGS. 13A and 13B are explanatory diagrams describing an operation ofthe optical element 10 according to the second embodiment;

FIG. 14 is an explanatory diagram describing an operation of the opticalelement 10 according to a third embodiment;

FIG. 15 is an explanatory diagram describing an operation of the opticalelement 10 according to the third embodiment;

FIGS. 16A to 16C are explanatory diagrams describing an operation of theoptical element 10 according to a fourth embodiment;

FIGS. 17A and 17B are explanatory diagrams describing an operation ofthe optical element 10 according to a fifth embodiment;

FIG. 18 is a plan view of a first electrode 18;

FIG. 19 is an explanatory diagram describing an operation of the opticalelement 10 according to a sixth embodiment;

FIG. 20 is an explanatory diagram describing an operation of the opticalelement 10 according to the sixth embodiment; and

FIG. 21 is an explanatory diagram describing an operation of the opticalelement 10 according to the sixth embodiment.

DETAILED DESCRIPTION First Embodiment

The operational principle of liquid movement by an electric field willbe first described.

FIG. 1A is a section diagram describing the principle of liquidmovement, and FIG. 1B is a view on the arrows A in FIG. 1A.

As shown in FIGS. 1A and 1B, a holding chamber 1 is tightly enclosed byfirst and second end walls 1A and 1B facing against each other andhaving a space g therebetween in the direction that light passes throughand side walls 1C connecting the first and second end walls 1A and 1B.

A first electrode 2 is provided on the entire inner surface of the firstend wall 1A, and the surface where the first electrode 2 faces theholding chamber 1 is covered by a water-repellent film 3A.

A second electrode 4 is provided on the inner surface of the second endwall 1B, and the second electrode 4 includes two electrode bodies 4A and4B aligned along a virtual axis L extending in the direction orthogonalto the direction in which the first and second end walls 1A and 1B faceagainst each other.

The entire areas of the surfaces of the two electrode bodies 4A and 4Band the inner surface of the second end wall 1B are covered by aninsulating film 5, and the entire area of the surface of the insulatingfilm 5 facing the holding chamber 1 is covered by a water-repellent film3B.

A first liquid 6 and a second liquid 7 are filled in the holding chamber1. The first liquid 6 is polar or conductive, and the second liquid 7 isfilled around the first liquid 6 and does not mutually mix with thefirst liquid 6.

The first electrode 2 faces the first liquid 6 through thewater-repellent film 3A, and the second electrode 4 faces the firstliquid 6 through the insulating film 5 and the water-repellent film 3B.

The first electrode 2 and the two electrode bodies 4A and 4B of thesecond electrode 4 are initially both grounded, and the first liquid 6at that state is positioned across the entire area of the one electrodebody 4A and the part of the other electrode body 4B which is closer tothe electrode body 4A.

At this state, the first liquid 6 has a round form at the plane visionas indicated by the solid line in the FIGS. 1A and 1B due to the surfacetension.

When a voltage E is applied to the other electrode body 4B here, thepart where the insulating film 5 faces the first liquid 6 is positivelycharged. Thus, an electric field (electrostatic force) is applied to thepart where the first liquid 6 faces the insulating film 5, and negativecharges, that is, the molecules of the first liquid 6 are pulled to theposition where the first liquid 6 faces the insulating film 5.

Then, the first liquid 6 changes the form as being pulled toward theelectrode body 4B as indicated by the broken lines in FIGS. 1A and 1B.In the end, all of the first liquid 6 surrounded by the second liquid 7moves from the above of the one electrode body 4A to the above of theother electrode body 4B in the direction of the extension of the virtualaxis L.

The water-repellent films 3A and 3B act for reducing the resistance ofthe first liquid 6, which is caused between the liquid 6 and the firstand second end walls 1A and 1B when the first liquid 6 moves above thefirst and second electrodes 2 and 4, such that the first liquid 6 canmove thereabove easily.

In this way, the polar or conductive first liquid 6 is moved by applyingan electric field to the first liquid 6 by the first and secondelectrodes 2 and 4.

Next, an optical element 10 of this embodiment will be described.

According to this embodiment, the optical element 10 functions as ashutter.

FIG. 2A is a longitudinal section diagram showing a construction of theoptical element 10, and FIG. 2B is a view on the arrows A in FIG. 2A.

FIG. 3A is a section diagram taken by the line B-B in FIG. 2A, and FIG.3B is a view on the arrows C in FIG. 2A.

FIGS. 4, 5 and 6 are explanatory diagrams describing operations of theoptical element 10.

As shown in FIGS. 2A and 2B, the optical element 10 includes a container12, a first liquid 14, a second liquid 16, a first electrode 18 and asecond electrode 20, and a voltage application section 22 (see FIG. 4).

The container 12 has first and second end walls 24 and 26 facing andextending against each other in parallel, side walls 28 connecting thefirst and second end walls 24 and 26 and a holding chamber 30 tightlyenclosed by the first and second end walls 24 and 26 and the side walls28.

The first and second end walls 24 and 26 contain an insulating material,and the first and second end walls 24 and 26 contain a clear materialthat allows light to pass through.

The first and second end walls 24 and 26 may contain a clear andinsulating synthetic resin material or a clear glass material, forexample.

The expression, “the direction of thickness of the container 12”, refersto the direction in which the first end wall 24 and the second end wall26 face against each other and which is the direction that light passesthrough the optical element 10.

According to this embodiment, the first and second end walls 24 and 26have a same rectangular plate form in a same size. The side walls 28have a rectangular frame form along the contours of the first and secondend walls 24 and 26. The holding chamber 30 has a flat column form, andthe holding chamber 30 has a uniform rectangular section extending inthe direction orthogonal to the direction that light passes through.

The holding chamber 30 includes an adjustment chamber and multiplelay-by chambers 34. In other words, the adjustment chamber 32 and themultiple lay-by chambers 34 have the first and second end walls 24 and26 facing against each other in the direction that light passes through.

The adjustment chamber 32 is used for adjusting the amount oftransmitted light based on the presence of the first liquid 14. Thelay-by chambers 34 connect to the adjustment chamber 32 and can hold thefirst liquid 14 laid by from the adjustment chamber 32.

According to this embodiment, the adjustment chamber positions at thecenter of the holding chamber 30 in the direction of the extension. Thelay-by chambers 34 are provided on both sides of the holding chamber 30in the direction of the extension. According to this embodiment, thedirection of the extension of the holding chamber 30 is parallel to thedirection of the long side of the container 12.

In other words, the two lay-by chambers 34 connect to the adjustmentchamber 32 from the direction orthogonal to the direction that lightpasses through and are provided on both sides of the adjustment chamber32 and on the straight line extending in the direction orthogonal to thedirection that light passes through.

The first liquid 14 is polar or conductive and is filled in the holdingchamber 30.

The second liquid 16 does not mutually mix with the first liquid 14 andis filled around the first liquid 14 in the holding chamber 30.

The first liquid 14 and the second liquid 16 substantially have an equalspecific gravity, and the transmittance of the first liquid 14 is lowerthan the transmittance of the second liquid 16.

According to this embodiment, the first liquid 14 is formed by mixingfine particles containing a material that does not allow light to passthrough into a liquid containing a mix of pure water, ethanol andethylene glycol, for example.

The fine particles may include carbon black. If carbon black is usedtherefor, hydrophilic coating processing is preferably performed on thesurface of the carbon black such that the carbon black can be uniformlymixed into the first liquid 14. The hydrophilic coating processing maybe performed by forming a hydrophilic group on the surface of the carbonblack, for example.

According to this embodiment, the second liquid 16 contains a clearsilicon oil.

The use of one with a low viscosity as the silicon oil contained in thesecond liquid 16 can reduce the viscous drag between the first andsecond liquids 14 and 16 and alleviate the friction between the firstliquid 14 and the first and second end walls 24 and 26, which isadvantageous for the improvement in the response property by an increasein speed of movement of the first liquid 14.

The liquid which can be used as the first liquid 14 is not limited tothe one in this embodiment but may be nitromethane, acetic anhydride,methyl acetate, ethyl acetate, methanol, acetonitrile, acetone, ethanol,propionitrile, tetrohydrofuran, n-hexane, 2-propanol, 2-butanone,n-butyronitrile, 1-propanol, 1-butanol, dimethyl sulfoxide,chlorobenzene, ethylene glycole, formamide, nitrobenzene, propylenecarbonate, 1,2-dichloroethane, carbonate disulfide, chloroform,bromobenzene, carbon tetrachloride, trichloroacetic acid anhydride,toluene, benzene, ethylenediamine, N,N-dimethylacetamide,N,N-dimethylformamide, tributyl phosphate, pyridine, benzonitrile,aniline, 1,4-dioxane or hexamethylphosphoramide, for example.

The liquid applicable as the second liquid 16 may be silicon, decanebase, octane base, nonane or heptane, for example.

Each of the first liquid 14 and the second liquid 16 may be a singleliquid or a mix of multiple liquids. In other words, the first liquid 14and the second liquid 16 may be only required to have a substantiallyequal specific gravity.

The first and second electrodes 18 and 20 are used for applying anelectric field to the first liquid 14.

As shown in FIGS. 2A and 3A, the first electrode 18 is provided on thefirst end wall 24 of the adjustment chamber and two lay-by chambers 34.According to this embodiment, the first electrode 18 includes a singleelectrode member 36 extending across the first end wall 24 of theadjustment chamber 32 and two lay-by chambers 34. According to thisembodiment, as shown in FIG. 3A, the electrode member 36 has rectangularcontours, which is one-size-smaller than the contours of the first endwall 24.

As shown in FIGS. 2A and 3B, the second electrode 20 is provided on thesecond end wall 26 of the adjustment chamber and two lay-by chambers 34.According to this embodiment, the second electrode 20 includes threeseparate electrode members 38, 40 and 42. One electrode member 40 of thethree electrode members 38, 40 and 42 is provided to the second end wall26 of the adjustment chamber 32, and the remaining two electrode members38 and 42 are provided to the two lay-by chambers 34.

These three electrode members 38, 40 and 42 are placed along a straightline extending in the direction orthogonal to the direction that lightpasses through. According to this embodiment, the straight line isparallel to the direction of the long side of the container 12.

According to this embodiment, as shown in FIG. 3B, the three electrodemembers 38, 40 and 42 have a same form in a same size and are equallyspaced apart from each other.

The mutually adjacent edges of the electrode members 38, 40 and 42 havepits and projections 2010 extending in the direction orthogonal to thedirection of the extension of the straight line. The adjacent electrodemembers are placed where the pits and projections 2010 are parallel to,are spaced apart from and face against each other. According to thisembodiment, the pits and projections 2010 have a triangular waveformwith a uniform amplitude.

The first and second electrodes 18 and 20, that is, the electrodemembers 36, 38, 40 and 42 may contain a conductive material such as anITO film (Indium Tin Oxide film) that allows light to pass through, forexample.

In FIGS. 3A and 3B, a wiring section 1802 extends from the electrode 36,and a wiring section 2002 extends from the electrode members 38, 40 and42.

As shown in FIG. 4, the voltage application section 22 is providedoutside of the container 12 and includes a ground terminal 2202electrically connecting to the first electrode 18 through the wiringsection 1802 (see FIG. 3A) and multiple voltage output terminals 2204electrically connecting to the electrode members 38, 40 and 42 of thesecond electrode 20 through the wiring section 2002 (see FIG. 3B).

The voltage application section 22 has a power supply 22A that outputs avoltage E and is configured to be capable of applying the voltage Eselectively to each of the electrode members 38, 40 and 42 of the secondelectrode 20 through the voltage output terminals 2204.

As shown in FIGS. 2A and 2B, an insulating film 44 is provided on theinternal surface of the second end wall 26 facing the holding chamber 30and the second electrode 20 on the internal surface.

Thus, voltage is applied between the first electrode and the secondelectrode 20, whereby the surface of the insulating film 44 may bepositively charged, for example. Hence, an electric field is applied tothe first liquid 14, and the electric field (electrostatic force) actson the molecules of the first liquid 14. As a result, the first liquid14 moves.

A clear water-repellent film 46 that allows light to pass through coversthe internal surface of the second end wall 26 and the entire area ofthe first electrode 18.

The water-repellent film 46 covers the internal surfaces of the sidewalls 28.

The water-repellent film 46 is configured such that the wettabilityagainst the second liquid 16 can be higher than the wettability againstthe first liquid 14. In other words, the angle of contact of the secondliquid 16 against the water-repellent film 46 is configured so as to besmaller than the angle of contact of the first liquid 14 against thewater-repellent film 46.

The water-repellent film 46 reduces the resistance caused between thefirst liquid 14 and the first and second end walls 24 and 26 when thefirst liquid 14 moves on the first and second electrodes 18 and 20 suchthat the first liquid 14 can move easily.

The water-repellent film 46 is a lipophilic film and may be formed byburning a material mainly containing silicon thereto or by forming afilm of a material containing amorphous fluoroplastics thereon, forexample. Various publicly known materials in the past may be adopted asthe water-repellent film 46.

Next, an operation of the optical element 10 will be described.

FIGS. 7A and 7B are explanatory diagrams describing an operation of theoptical element 10.

First of all, an operation will be described in a case that theadjustment chamber 32 of the optical element 10 changes from the statethat interrupts light to the state that allows light to pass through.

As shown in FIG. 4, the first liquid 14 is initially positioned betweenthe electrode member 36 of the first electrode 18 and the centralelectrode member 40 of the second electrode 20 in the adjustment chamber32.

Under this state, the voltage application section 22 applies the voltageE to the central electrode member 40 and opens (or applies the groundpotential to) the remaining two electrode members 38 and 42.

Thus, the electric field by the voltage E applied to the first electrode18 and central electrode member 40 acts on the first liquid 14 facingthe central electrode member 40, whereby the first liquid 14 does notmove and can be held at the position. As a result, a most part of thefirst liquid 14 faces the central electrode member 40, and parts of thefirst liquid 14 face the adjacent two electrode members 38 and 42.

Under this condition, as shown in FIG. 7B, the incident light travelingtoward the adjustment chamber 32 is interrupted by the first liquid 14positioned in the adjustment chamber 32 and having a low transmittance.

Next, as shown in FIG. 5, the voltage application section 22 opens (orapplies the ground potential to) the central electrode member 40 andapplies the voltage E to the remaining two electrode members 38 and 42.In other words, the position subject to the voltage application to thesecond electrode 20 is changed to the remaining two electrode members 38and 42.

Then, as shown in FIG. 5, the electric field by the voltage E applied tothe first electrode 18 and two electrode members 38 and 42 acts on thefirst liquid 14 facing the central electrode member 40, whereby the halfof the first liquid 14 surrounded by the second liquid 16 moves towardone of the lay-by chambers 34, and, at the same time, the other half ofthe first liquid 14 moves toward the other lay-by chamber 34.

Thus, as shown in FIG. 6, the first liquid 14 is divided into two, whichare then held by the two lay-by chambers 34. Therefore, the half of thefirst liquid 14 is held in one of the lay-by chambers 34, and theremaining half of the first liquid 14 is held in the other lay-bychamber 34.

In this case, a most part of the one divided first liquid 14 faces theelectrode member 38 on one side, and a part of the divided first liquid14 faces the adjacent central electrode member 40. A most part of theother divided first liquid 14 faces the electrode member 42 on the otherside, and a part of the other divided first liquid 14 faces the adjacentcentral electrode member 40.

Under this condition, as shown in FIG. 7A, the incident light travelingtoward the adjustment chamber 32 passes through the second liquid 16positioned in the adjustment chamber 32 and having a high transmittance.

Next, an operation will be described in a case that the adjustmentchamber 32 of the optical element 10 changes from the state that allowslight to pass through to the state that interrupts light, conversely tothe above.

As shown in FIG. 6, the divided first liquids 14 are held in the twolay-by chambers 34. Under this state, the voltage application section 22applies the voltage E to the central electrode member 40 and opens (orapplies the ground potential to) the remaining two electrode members 38and 42.

Thus, as shown in FIG. 5, the electric field by the voltage E applied tothe first electrode 18 and central electrode member 40 acts on thedivided first liquids 14 facing the two electrode members 38 and 42,whereby the divided first liquids 14 surrounded by the second liquid 16move from the lay-by chambers 34 to the adjustment chamber 32.

Hence, as shown in FIG. 4, the two divided first liquids 14 are held byand combined in the adjustment chamber 32.

Therefore, the electric field by the voltage E applied to the firstelectrode 18 and central electrode member 40 acts on the first liquid14, whereby the first liquid 14 does not move and can be held at theposition facing the central electrode member 40. As a result, a mostpart of the first liquid 14 faces the central electrode member 40, andparts of the first liquid 14 face the adjacent two electrode members 38and 42.

Under this condition, as shown in FIG. 7B, the incident light travelingtoward the adjustment chamber 32 is interrupted by the first liquid 14positioned in the adjustment chamber 32 and having a low transmittance.

In this way, the adjustment chamber 32 is allowed to pass lighttherethrough by changing the position subject to the voltage applicationby the voltage application section 22 and dividing and moving the firstliquid 14 from the adjustment chamber 32 to the two lay-by chambers 34.Furthermore, the first liquids 14 laid by in the two lay-by chambers 34are moved and combined, whereby the adjustment chamber 32 interruptslight. As a result, the optical element 10 can be functioned as ashutter.

Next, a case will be described in which the optical element 10 isprovided as a shutter in a shooting optical system of an imagingapparatus, such as a digital still camera and a video camera.

FIG. 8 is a block diagram showing a construction of the imagingapparatus 100, and FIG. 9 is a diagram showing a construction of ashooting optical system 104 of the imaging apparatus 100.

As shown in FIG. 8, the imaging apparatus 100 has an external case, notshown, and the case has a lens barrel 102 built in and further has adisplay 112, a shutter button and operation switches 116 on the surfaceof the case. The operation switches 116 are used for performing variousoperations relating to and shooting.

The shooting optical system 104 and an imaging element 106 are mountedon the lens barrel 102. The imaging element 106 images a subject imagecaptured by the shooting optical system 104.

The imaging apparatus 100 includes an image processing section 110, adisplay control section 114 and a control section 118. The imageprocessing section 110 creates image data based on imaged signals outputfrom the imaging element 106 and records it in a recording medium 108such as a memory card. The display control section 114 causes thedisplay 112 to display the image data. The control section 118 includesa CPU that controls the image processing section 110 and the displaycontrol section 114 in accordance with an operation on the shutterbutton and/or the operation switches 116.

As shown in FIG. 9, the shooting optical system 104 has, on an opticalaxis G, a first lens group 120, a second lens group 122, a third lensgroup 124, a fourth lens group 126 and a filter group 128 in order froma subject to the imaging element 106.

In this example, the first lens group 120 and third lens group 124 arenot movable in the direction of the optical axis, and the second lensgroup 122 is movable in the direction of the optical axis as a zoomlens. The fourth lens group 126 is movable in the direction of theoptical axis as a focus lens.

The pencils of light from a subject conducted by the first lens group120 become parallel pencils of light by the second lens group 122, areconducted to the third lens group 124 and are converged to an imagingplane 106A of the imaging element 106 through the fourth lens group 126and filter group 128.

The optical element 10 is placed between the filter group 128 and theimaging element 106, and the first liquid 14 is moved keeping theadjustment chamber 32 on the optical axis G and the direction that lightpasses through in parallel with the optical axis G. Thus, the firstliquid 14 can interrupt the pencils of light to be conducted to theimaging element 106.

Therefore, in the optical element 10, when the pencils of light areinterrupted by the moved first liquid 14, the time for the irradiationto the imaging plane 106A, that is, the exposure time of the imagingelement 106 can be controlled.

Notably, the cross-sectional area of the pencils of light of the subjectimage converged by the shooting optical system 104 decreases as thedistance between the shooting optical system 104 and the imaging plane106A of the imaging element 106 decreases. Therefore, like in thisembodiment, the cross-sectional area of the pencils of light opened andinterrupted by the optical element 10 decreases when the optical element10 is placed immediately before the imaging element 106A of the imagingelement 106. Therefore, the travel of the first liquid 14 can bereduced, which is advantageous for the reduction of the size of theoptical element 10 and the improvement of the response property.

As described above, according to this embodiment, the first liquid 14held in the adjustment chamber 32 is divided by the electric fieldapplied from the electrode members 38 and 42 in the lay-by chambers 34and is moved to the lay-by chambers 34. Furthermore, the divided firstliquids 14 held in the lay-by chambers 34 are moved and combined fromthe lay-by chambers 34 to the adjustment chamber 32 by the electricfield applied from the electrode member 40 in the adjustment chamber 32.

Thus, since the divided first liquids 14 are moved, the mass and travelof the first liquids 14 can be reduced more than those in the case thatthe entire first liquid 14 is moved. Therefore, the speed of themovement of the first liquid 14 can be increased, which is advantageousfor the improvement of the response property of the optical element 10.

Next, a comparison example will be described.

FIG. 10A is a diagram describing a movement of the first liquid 14 inthe comparison example, and FIG. 10B is a diagram describing themovement of the first liquid 14 according to this embodiment.

As shown in FIG. 10B, in the optical element 10 of this embodiment, thefirst liquid 14 is divided into two, which then move between theadjustment chamber 32 and the lay-by chambers 34.

As shown in FIG. 10A, in the optical element 10 in the comparisonexample, the first liquid 14 having an equal volume to that of the firstliquid 14 in the optical element 10 according to this embodiment movesentirely between the adjustment chamber 32 and one of the lay-bychambers 34.

Thus, according to this embodiment, the volume and mass of the dividedfirst liquids 14 are the half of the first liquid 14 in the comparisonexample if the volumes of the first liquids 14 are equal.

In the comparison example, the travel, which may be required by thefirst liquid 14 for moving on the adjacent electrode member, issubstantially equal to the diameter (liquid diameter) of the firstliquid 14.

On the other hand, according to this embodiment, the travel, which maybe required by the divided first liquids 14 for moving onto the adjacentelectrode members and combining, is substantially equal to the half ofthe travel in the comparison example.

According to this embodiment, since the volume of the divided firstliquid 14 is the half of that in the comparison example, the diameter ofthe first liquid 14 is much smaller than that in the comparison example.Therefore, the travel that the first liquid 14 is to move issignificantly reduced in comparison with the travel that the firstliquid 14 to move in the comparison example.

If the electric fields to be applied thereto are identical, the movementspeed increases as the mass of the first liquid 14 decreases.

Therefore, in the optical element 10 of this embodiment, the travel andmass of the first liquid 14 are smaller than those in the comparisonexample, which is advantageous for increasing the speed of the movementof the first liquid 14.

In this embodiment, the edges where the electrode members 38, 40 and 42are adjacent to each other have the extension of the pits andprojections 2010 in the direction orthogonal to the direction of theextension of the straight line, and the adjacent electrode members havethe pits and projections 2010 in parallel and facing against each other.

Thus, even when the dimension of the space between the electrode membersis equal to or slightly larger than the diameter of the first liquid 14,a part of the first liquid 14 in the direction of the movement can befaced against the adjacent electrode member keeping a most part of thefirst liquid 14 positioned at one of the electrode members, which isadvantageous for increasing the spaces between electrode members.

While the form of the pits and projections 2010 may be a triangularwaveform having substantially uniform amplitudes like in thisembodiment, the same effect as above can be apparently provided evenwhen the form of the pits and projections 2010 is a square waveformhaving substantially uniform amplitudes, as shown in FIG. 11A.

Furthermore, as shown in FIG. 11B, the electrode member 40 on the endwall 26 of the adjustment chamber 32 has projections 2012 at the centerof the pits and projections 2010 in the direction of the extension. Theprojections 2012 more largely project toward the end wall 26 of thelay-by chambers 34 than the other projections of the pits andprojections 2010. The electrode members 38 and 42 on the end wall 26 ofthe lay-by chambers 34 have pits 2014 at the center of the pits andprojections 2010 in the direction of the extension. The pits 2014 morelargely recess toward the center of the lay-by chambers 34 than otherpits of the pits and projections 2010. The projections 2012 and pits2014 spaced apart from and facing against each other provide followingeffects.

That is, when the first liquids 14 on the electrode members 38 and 42 inthe lay-by chambers 34 move toward the electrode member 40 in theadjustment chamber 32, the pits 2012 have wider contact with the firstliquids 14 than the other pits and projections 2010 of the centralelectrode member 40. Thus, an electric field can be strongly applied onthe first liquids 14 from the projections 2012.

Hence, the center part of the first liquids 14 can be moved to theelectrode member 40 in the adjustment chamber 32 earlier than the otherparts. Therefore, the first liquids 14 can be moved more smoothly, whichis advantageous for increasing the speed of the movement of the firstliquid 14 from the lay-by chambers 34 to the adjustment chamber 32.

Notably, in order to apply an electric field to the first liquids 14, apart of the first liquids 14 may be only required to face the adjacentelectrode member, keeping a most part of the first liquids 14 on one ofthe electrode members. Apparently, the pits and projections 2010 may notbe provided at the positions where the electrode members 38, 40 and 42are adjacent to each other, and the electrode members 38, 40 and 42 maybe aligned straight in the direction orthogonal to the direction of theextension of the straight line. However, the existence of the pits andprojections 2010 is advantageous for increasing the speed of themovement, as described above.

Second Embodiment

A second embodiment will be described next.

The second embodiment is different from the first embodiment in that thefirst liquid 14 is clear and the transmittance of the second liquid 16is lower than the transmittance of the first liquid 14.

FIG. 12 is a longitudinal section diagram showing a construction of anoptical element 10 of the second embodiment. FIGS. 13A and 13B areexplanatory diagrams describing an operation of the optical element 10of the second embodiment. The same reference numerals are given to thesame or similar parts and components as those of the first embodiment inthe following descriptions on this embodiment.

As shown in FIG. 12, the optical element 10 includes the container 12,the first liquid 14, the second liquid 16, the first electrode 18 andthe second electrode 20, and the voltage application section 22, likethe first embodiment.

The first liquid 14 is polar or conductive and is filled in the holdingchamber 30.

The second liquid 16 does not mutually mix with the first liquid 14 andis filled around the first liquid 14 in the holding chamber 30.

The first liquid 14 and the second liquid 16 substantially have an equalspecific gravity, and the transmittance of the second liquid 16 is lowerthan the transmittance of the first liquid 14.

According to this embodiment, the first liquid 14 is a liquid containinga mix of pure water, ethanol and ethylene glycol. The second liquid 16is a clear silicon oil and contains fine particles containing a materialthat does not allow light to pass through.

The container 12, first electrode 18 and second electrode 20 and voltageapplication section 22 have the same constructions as those of the firstembodiment.

Next, operations of the optical element 10 will be described.

First of all, an operation will be described in a case that theadjustment chamber 32 of the optical element 10 changes from the statethat allows light to pass therethrough to the state that interruptslight.

As shown in FIGS. 12 and 13A, the first liquid 14 is initiallypositioned between the electrode member 36 of the first electrode 18 andthe central electrode member 40 of the second electrode 20 in theadjustment chamber 32.

Under this state, the voltage application section 22 applies a voltage Eto the central electrode member 40 and opens (or applies the groundpotential to) the remaining two electrode members 38 and 42.

Thus, the electric field by the voltage E applied to the first electrode18 and central electrode member 40 acts on the first liquid 14 facingthe central electrode member 40, whereby the first liquid 14 does notmove and can be held at the position. As a result, a most part of thefirst liquid 14 faces the central electrode member 40, and parts of thefirst liquid 14 face the adjacent two electrode members 38 and 42.

Under this condition, as shown in FIG. 13A, the incident light travelingtoward the adjustment chamber 32 passes through the first liquid 14positioned in the adjustment chamber 32 and having a high transmittance.

Next, the voltage application section 22 opens (or applies the groundpotential to) the central electrode member 40 and applies the voltage Eto the remaining two electrode members 38 and 42. In other words, theposition subject to the voltage application to the second electrode 20is changed to the remaining two electrode members 38 and 42.

Then, as shown in FIG. 13B, the electric field by the voltage E appliedto the first electrode 18 and two electrode members 38 and 42 acts onthe first liquid 14 facing the central electrode member 40, whereby thehalf of the first liquid 14 surrounded by the second liquid 16 movestoward one of the lay-by chambers 34, and, at the same time, the otherhalf of the first liquid 14 moves toward the other lay-by chamber 34.

Thus, the first liquid 14 is divided into two, which are then held bythe two lay-by chambers 34. Therefore, the half of the first liquid 14is held in one of the lay-by chambers 34, and the remaining half of thefirst liquid 14 is held in the other lay-by chamber 34.

In this case, a most part of the one divided first liquid 14 faces theelectrode member 38 on one side, and a part of the divided first liquid14 faces the adjacent central electrode member 40. A most part of theother divided first liquid 14 faces the electrode member 42 on the otherside, and a part of the other divided first liquid 14 faces the adjacentcentral electrode member 40.

Under this condition, as shown in FIG. 13B, the incident light travelingtoward the adjustment chamber 32 is interrupted by the second liquid 16positioned in the adjustment chamber 32 and having a low transmittance.

Next, an operation will be described in a case that the adjustmentchamber 32 of the optical element 10 changes from the state thatinterrupts light to the state that allows light to pass therethrough,conversely to the above.

The divided first liquids 14 are held in the two lay-by chambers 34.Under this state, the voltage application section 22 applies the voltageE to the central electrode member 40 and opens (or applies the groundpotential to) the remaining two electrode members 38 and 42.

Thus, as shown in FIG. 13B, the electric field by the voltage E appliedto the first electrode 18 and central electrode member 40 acts on thedivided first liquids 14 facing the two electrode members 38 and 42,whereby the divided first liquids 14 surrounded by the second liquid 16move from the lay-by chambers 34 to the adjustment chamber 32.

Hence, as shown in FIG. 13A, the two divided first liquids 14 are heldby and combined in the adjustment chamber 32.

Therefore, the electric field by the voltage E applied to the firstelectrode 18 and central electrode member 40 acts on the first liquid14, whereby the first liquid 14 does not move and can be held at theposition facing the central electrode member 40. As a result, a mostpart of the first liquid 14 faces the central electrode member 40, andparts of the first liquid 14 face the adjacent two electrode members 38and 42.

Under this condition, as shown in FIG. 13A, the incident light travelingtoward the adjustment chamber 32 is allowed to pass through the firstliquid 14 positioned in the adjustment chamber 32 and having a lowtransmittance.

Like the first embodiment, the optical element 10 according to thesecond embodiment can be functioned as a shutter by switching theadjustment chamber 32 between the state that allows light to passtherethrough and the state that interrupts light by changing theposition subject to the voltage application by the voltage applicationsection 22 and dividing and moving the first liquid 14 between theadjustment chamber 32 and the two lay-by chambers 34.

Therefore, also according to this embodiment, the speed of the movementof the first liquid 14 can be increased, which is advantageous for theimprovement of the response property of the optical element 10, like thefirst embodiment.

Third Embodiment

A third embodiment will be described next.

The third embodiment is different from the first embodiment in that thenumber of the lay-by chambers 34 is four and that the first liquid 14 isdivided into four and is moved between the adjustment chamber 32 and thelay-by chambers 34.

FIGS. 14 and 15 are explanatory diagrams describing an operation of theoptical element 10 according to the third embodiment and are plan viewsof the optical element 10.

As shown in FIG. 14, the four lay-by chambers 34 are aligned with anequal pitch (90 degrees) around the adjustment chamber 32 in thecircumferential direction at the sight from the direction that lightpasses through.

In other words, the holding chamber 30 is crossshaped at the sight fromthe direction that light passes through, and the adjustment chamber 32is positioned at the center of the cross shape. Two of the four lay-bychambers 34 are provided on a straight line extending in the directionorthogonal to the direction that light passes through on both sides ofthe adjustment chamber 32. The remaining two lay-by chambers 34 areprovided on another straight line orthogonal to the straight line in thedirection orthogonal to the direction that light passes through on bothsides of the adjustment chamber 32.

The adjustment chamber 32 and four lay-by chambers 34 include a firstend wall (not shown) and a second end wall 26, which face against eachother in the direction that light passes through.

The four lay-by chambers 34 further include side walls 28 connecting thefirst and second end walls. In each of the lay-by chambers 34, the firstand second end walls are divided by the side wall 28 excluding the partsconnecting to the adjustment chamber 32.

Then, the side walls 28 of the adjacent lay-by chambers 34 form a corner2802 extending between the first and second end walls at the positionconnecting to the adjustment chamber 32. According to this embodiment,the corner 2802 makes a right angle.

According to the third embodiment, like the first embodiment, the firstliquid 14 and the second liquid 16 substantially have an equal specificgravity, and the transmittance of the first liquid 14 is lower than thetransmittance of the second liquid 16. The second liquid 16 is filledaround the first liquid 14 in the holding chamber 30.

As shown in FIG. 14, the first electrode 18 is provided on the first endwall of the adjustment chamber 32 and four lay-by chambers 34. The firstelectrode 18 includes a single electrode member 36 extending across thefirst end wall of the adjustment chamber 32 and four lay-by chambers 34.According to this embodiment, the electrode member 36 has a cross shapehaving one-size-smaller contours than the contours of the first endwall.

The second electrode 20 is provided on the second end wall 26 of theadjustment chamber 32 and four lay-by chambers 34. According to thisembodiment, the second electrode 20 includes five electrode members 50A,50B, 50C, 50D and 50E in a same form and a same size, which areseparated from each other. The one electrode member 50A of the fiveelectrode members is provided on the second end wall 26 of theadjustment chamber 32, and the remaining four electrode members 50B,50C, 50D and 50E are provided on the second end wall 26 of the fourlay-by chambers 34.

The edges where the central electrode member 50A and the four electrodemembers 50B, 50C, 50D and 50E are adjacent to each other have pits andprojections 2010 extending in the direction orthogonal to the directionof the extension of the straight lines. The adjacent electrode membersare placed with the pits and projections 2010 parallel to, spaced apartfrom and facing against each other.

The voltage application section 22 supplies the ground potential to thefirst electrode 18 and is configured to be capable of applying thevoltage E selectively to each of the five electrode members 50A, 50B,50C, 50D and 50E of the second electrode 20.

Next, operations of the optical element 10 will be described.

First of all, an operation will be described in a case that theadjustment chamber 32 of the optical element 10 changes from the statethat interrupts light to the state that allows light to passtherethrough.

As shown in FIG. 14, the first liquid 14 is initially positioned betweenthe electrode member 36 of the first electrode 18 and the centralelectrode member 50A of the second electrode 20 in the adjustmentchamber 32.

Under this state, the voltage application section 22 applies the voltageE to the central electrode member 50A and opens (or applies the groundpotential to) the remaining four electrode members 50B, 50C, 50D and50E.

Thus, the electric field by the voltage E applied to the first electrode18 and central electrode member 50A acts on the first liquid 14 facingthe central electrode member 50A, whereby the first liquid 14 does notmove and can be held at the position. As a result, a most part of thefirst liquid 14 faces the central electrode member 50A, and parts of thefirst liquid face the adjacent four electrode members 50B, 50C, 50D and50E.

Under this condition, the incident light traveling toward the adjustmentchamber 32 is interrupted by the first liquid 14 positioned in theadjustment chamber 32 and having a low transmittance.

Next, as shown in FIG. 15, the voltage application section 22 opens (orapplies the ground potential to) the central electrode member 50A andapplies the voltage E to the remaining four electrode members 50B, 50C,50D and 50E. In other words, the position subject to the voltageapplication to the second electrode 20 is changed to the remaining fourelectrode members 50B, 50C, 50D and 50E.

Then, the electric field by the voltage E applied to the first electrode18 and four electrode members 50B, 50C, 50D and 50E acts on the firstliquid 14 facing the central electrode member 50A, whereby the firstliquid 14 surrounded by the second liquid 16 is divided into four andmoves toward the four lay-by chambers 34.

Thus, the first liquid 14 is divided into four, which are then held bythe four lay-by chambers 34.

In this case, most parts of the divided first liquids 14 face therespective four electrode members 50B, 50C, 50D and 50E, and parts ofthe divided first liquids 14 face the adjacent central electrode member50A.

Under this condition, the incident light traveling toward the adjustmentchamber 32 passes through the second liquid 16 positioned in theadjustment chamber 32 and having a high transmittance.

Next, an operation will be described in a case that the adjustmentchamber 32 of the optical element 10 changes from the state that allowslight to pass therethrough to the state that interrupts light,conversely to the above.

As shown in FIG. 15, the divided first liquids 14 are held in the fourlay-by chambers 34. Under this state, the voltage application section 22applies the voltage E to the central electrode member 50A and opens (orapplies the ground potential to) the remaining four electrode members50B, 50C, 50D and 50E.

Thus, the electric field by the voltage E applied to the first electrode18 and central electrode member 50A acts on the first liquids 14 facingthe four electrode members 50B, 50C, 50D and 50E, whereby the dividedfirst liquids 14 surrounded by the second liquid 16 move from the lay-bychambers 34 to the adjustment chamber 32.

Hence, as shown in FIG. 14, the four divided first liquids 14 are heldby and combined in the adjustment chamber 32.

Therefore, the electric field by the voltage E applied to the firstelectrode 18 and central electrode member 50A acts on the first liquid14, whereby the first liquid 14 does not move and can be held at theposition facing the central electrode member 50A. As a result, a mostpart of the first liquid 14 faces the central electrode member 50A, andparts of the first liquid 14 face the adjacent four electrode members50B, 50C, 50D and 50E.

Under this condition, the incident light traveling toward the adjustmentchamber 32 is interrupted by the first liquid 14 positioned in theadjustment chamber 32 and having a low transmittance.

Like the first embodiment, the optical element 10 according to the thirdembodiment can be functioned as a shutter by switching the adjustmentchamber 32 between the state that allows light to pass therethrough andthe state that interrupts light by changing the position subject to thevoltage application by the voltage application section 22 and dividingand moving the first liquid 14 between the adjustment chamber 32 and thefour lay-by chambers 34.

According to the third embodiment in particular, since the first liquid14 is divided into four, the speed of the movement of the first liquid14 can be increased more than that of the first embodiment, which isadvantageous for the improvement of the response property of the opticalelement 10.

Furthermore, according to the third embodiment, since the four corners2802 face the holding chamber 30, the first liquid 14 can be smoothlydivided by separating the first liquid by the corners 2802 when thefirst liquid 14 held in the adjustment chamber 32 is divided and movedto the lay-by chambers 34, which is advantageous for the increase inmovement speed of the first liquid 14.

Notably, the first liquid 14 can be divided and moved even when theholding chamber 30 does not have the corners 2802. However, theexistence of the corners 2802 is more advantageous for the increase inmovement speed of the first liquid 14 as described above than the casewithout the corners 2802.

Fourth Embodiment

A fourth embodiment will be described next.

The fourth embodiment is a variation example of the third embodiment andis different from the third embodiment in the operation for dividing thefirst liquid 14 into two while the construction is identical to that ofthe third embodiment.

FIGS. 16A, 16B and 16C are explanatory diagrams describing an operationof the optical element 10 according to the fourth embodiment.

As shown in FIG. 16A, the voltage application section 22 applies thevoltage E to the electrode members 50B and 50D of the facing two lay-bychambers 34, which opens (or applies the ground potential to) theelectrode members 50C and 50E in the remaining two lay-by chambers 34and the central electrode member 50A. Then, the first liquid 14 isdivided into two, which are then held in the two facing lay-by chambers34.

Under this condition, the incident light traveling toward the adjustmentchamber 32 passes through the second liquid 16 positioned in theadjustment chamber 32 and having a high transmittance.

Next, the voltage application section 22 applies the voltage E to thecentral electrode member 50A and opens (or applies the ground potentialto) the remaining four electrode members 50B, 50C, 50D and 50E.

Thus, as shown in FIG. 16B, the first liquids 14 surrounded by thesecond liquid 16 in the facing two lay-by chambers 34 move from thelay-by chambers 34 to the adjustment chamber 32. Then, the first liquids14 are held by and combined in the adjustment chamber 32.

Under this condition, the incident light traveling toward the adjustmentchamber 32 is interrupted by the first liquid 14 positioned in theadjustment chamber 32 and having a low transmittance.

Since the two first liquids 14 brought into contact with each other arecombined, the force acting on each of the first liquids 14 deforms thecombined first liquid 14 to a form stretched along the straight lineorthogonal to the straight line connecting the facing two lay-bychambers 34, that is, along the straight line connecting the remainingtwo lay-by chambers 34, as indicated by the chain double-dashed lines inFIG. 16B.

With the deformation, the voltage application section 22 applies thevoltage E to the electrode members 50C and 50 E in the remaining twolay-by chambers 34 and opens (or applies the ground potential to) theelectrode members 50B and 50D in the two lay-by chambers 34 and thecentral electrode member 50A. Thus, the first liquid 14 is divided intotwo by the action of the electric field by the voltage E applied to theelectrode members 50C and 50E in the remaining two lay-by chambers 34,which are then moved to and held by the remaining two lay-by chambers34, as shown in FIG. 16C.

Under this condition, the incident light traveling toward the adjustmentchamber 32 passes through the second liquid 16 positioned in theadjustment chamber 32 and having a high transmittance.

According to the fourth embodiment, after the first liquids 14 are movedfrom the facing two lay-by chambers 34 to the adjustment chamber 32 andare combined and deformed therein, the first liquids 14 are moved to theremaining two lay-by chambers 34 in the direction of the deformation.Thus, after the first liquid 14 is moved from the two facing lay-bychambers to the adjustment chamber 32, the first liquid 14 can bequickly moved to the remaining two lay-by chambers 34. Therefore, theperiod of time when the first liquid 14 stays in the adjustment chamber32 can be reduced, which is advantageous for the increase in speed ofthe operation for interrupting the optical path by the optical element10.

Fifth Embodiment

A fifth embodiment will be described next.

The fifth embodiment is another variation example of the thirdembodiment, and the number of lay-by chambers 34 is eight, and the firstliquid 14 is divided into eight.

FIGS. 17A and 17B are explanatory diagrams describing an operation ofthe optical element 10 according to the fifth embodiment, and FIG. 18 isa plan view of the first electrode 18.

As shown in FIG. 17A, the optical element 10 includes the holdingchamber 30, and the holding chamber 30 includes the adjustment chamber32 and the eight lay-by chambers 34 equally spaced apart around theperimeter of the adjustment chamber 32.

The adjustment chamber 32 and eight lay-by chambers 34 include a firstend wall (not shown) and a second end wall 26, which face against eachother in the direction that light passes through.

The eight lay-by chambers 34 further include side walls 28 connectingthe first and second end walls. In each of the lay-by chambers 34, thefirst and second end walls are divided by the side wall 28 excluding thepart connecting to the adjustment chamber 32.

Then, the side walls 28 of the adjacent lay-by chambers 34 form a corner2802 extending between the first and second end walls at the partconnecting to the adjustment chamber 32. According to this embodiment,each of the corners 2802 makes an acute angle.

According to the fifth embodiment, like the first embodiment, the firstliquid 14 and the second liquid 16 substantially have an equal specificgravity, and the transmittance of the first liquid 14 is lower than thetransmittance of the second liquid 16. The second liquid 16 is filledaround the first liquid 14 in the holding chamber 30.

As shown in FIG. 18, the first electrode 18 is provided on the first endwall of the adjustment chamber 32 and eight lay-by chambers 34. Thefirst electrode 18 includes a single electrode member 36 extendingacross the first end wall of the adjustment chamber 32 and eight lay-bychambers 34. According to this embodiment, the electrode member 36 hasone-size-smaller contours than the contours of the first end wall.

As shown in FIG. 17A, the second electrode 20 is provided on the secondend wall 26 of the adjustment chamber 32 and eight lay-by chambers 34.According to this embodiment, the second electrode 20 includes nineelectrode members, which are separated from each other. One electrodemember 50F of them is provided on the second end wall 26 of theadjustment chamber 32, and the remaining eight electrode members 50G ina same form and a same size are provided on the second end wall 26 ofthe eight lay-by chambers 34.

The voltage application section 22 supplies the ground potential to thefirst electrode 18 and is configured to be capable of applying thevoltage E selectively to each of the nine electrode members 50F and 50Gof the second electrode 20.

Next, operations of the optical element 10 will be described.

First of all, an operation will be described in a case that theadjustment chamber 32 of the optical element 10 changes from the statethat interrupts light to the state that allows light to passtherethrough.

As shown in FIG. 17A, the first liquid 14 is initially positionedbetween the electrode member 36 of the first electrode 18 and thecentral electrode member 50F of the second electrode 20 in theadjustment chamber 32.

Under this state, the voltage application section 22 applies the voltageE to the central electrode member 50F and opens (or applies the groundpotential to) the remaining eight electrode members 50G.

Thus, the electric field by the voltage E applied to the first electrode18 and central electrode member 50F acts on the first liquid 14 facingthe central electrode member 50F, whereby the first liquid 14 does notmove and can be held at the position. As a result, a most part of thefirst liquid 14 faces the central electrode member 50F, and parts of thefirst liquid 14 face the adjacent eight electrode members 50G.

Under this condition, the incident light traveling toward the adjustmentchamber 32 is interrupted by the first liquid 14 positioned in theadjustment chamber 32 and having a low transmittance.

Next, the voltage application section 22 opens (or applies the groundpotential to) the central electrode member 50F and applies the voltage Eto the remaining eight electrode members 50G. In other words, theposition subject to the voltage application to the second electrode 20is changed to the remaining eight electrode members 50G.

Then, the electric field by the voltage E applied to the first electrode18 and eight electrode members 50G acts on the first liquid 14 facingthe central electrode member 50F, whereby the first liquid 14 surroundedby the second liquid 16 is divided into eight, which then move towardthe eight lay-by chambers 34, as shown in FIG. 17B.

Thus, the first liquid 14 is divided into eight, which are then held bythe eight lay-by chambers 34.

In this case, a most part of the divided first liquid 14 faces the eightelectrode members 50G, and parts of the first liquid 14 face theadjacent central electrode member 50F.

Under this condition, the incident light traveling toward the adjustmentchamber 32 passes through the second liquid 16 positioned in theadjustment chamber 32 and having a high transmittance.

Next, an operation will be described in a case that the adjustmentchamber 32 of the optical element 10 changes from the state that allowslight to pass therethrough to the state that interrupts light,conversely to the above.

As shown in FIG. 17B, the divided first liquids 14 are held in the eightlay-by chambers 34. Under this state, the voltage application section 22applies the voltage E to the central electrode member 50F and opens (orapplies the ground potential to) the remaining eight electrode members50G.

Thus, the electric field by the voltage E applied to the first electrode18 and central electrode member 50F acts on the first liquids 14 facingthe eight electrode members 50G, whereby the divided first liquids 14surrounded by the second liquid 16 move from the lay-by chambers 34 tothe adjustment chamber 32.

Hence, as shown in FIG. 17A, the eight divided first liquids 14 are heldby and combined in the adjustment chamber 32.

Therefore, the electric field by the voltage E applied to the firstelectrode 18 and central electrode member 50F acts on the first liquid14, whereby the first liquid 14 does not move and can be held at theposition facing the central electrode member 50F. As a result, a mostpart of the first liquid 14 faces the central electrode member 50F, andparts of the first liquid 14 face the adjacent eight electrode members50G.

Under this condition, the incident light traveling toward the adjustmentchamber 32 is interrupted by the first liquid 14 positioned in theadjustment chamber 32 and having a low transmittance.

Like the first embodiment, the optical element 10 according to the fifthembodiment can be functioned as a shutter by switching the adjustmentchamber 32 between the state that allows light to pass therethrough andthe state that interrupts light by dividing and moving the first liquid14 between the adjustment chamber 32 and the eight lay-by chambers 34.

According to the fifth embodiment in particular, since the first liquid14 is divided into eight, the speed of the movement of the first liquid14 can be increased more than that of the first embodiment in which thefirst liquid 14 is divided into two or the third embodiment in which thefirst liquid 14 is divided into four. This is advantageous for theimprovement of the response property of the optical element 10.

Furthermore, since the eight corners 2802 face the holding chamber 30,the first liquid 14 can be smoothly divided by separating the firstliquid 14 by the corners 2802 when the first liquid 14 held in theadjustment chamber 32 is divided and moved to the lay-by chambers 34,like the third embodiment, which is advantageous for the increase inmovement speed of the first liquid 14.

Sixth Embodiment

A sixth embodiment will be described next.

According to the sixth embodiment, for the improvement of the responseproperty, the first liquid 14 is divided in two steps, and the dividedfirst liquids 14 are combined in one step.

FIGS. 19 to 21 are explanatory diagrams describing an operation of theoptical element 10 according to the sixth embodiment.

As shown in FIG. 19, the optical element 10 includes the container 12,the first liquid 14, the second liquid 16, the first electrode 18 andthe second electrode 20 and the voltage application section 22.

The container 12 has a first end wall (not shown) and a second end wall26 facing and extending against each other in parallel in the directionthat light passes through and side walls 28 connecting the first andsecond end walls 24 and 26 and a holding chamber 30 tightly enclosed bythe first and second end walls and the side walls 28.

The first electrode 18 is provided on the first end wall 24, and thesecond electrode 20 is provided on the second end wall 26.

The second electrode 20 includes a central electrode member 52 andmultiple surrounding electrode members 54 around the central electrodemember 52. According to this embodiment, three surrounding electrodemembers 54 each are provided on both sides of the central electrodemember 52. The three surrounding electrode members 54 include a firstsurrounding electrode member 54A at the center and two secondsurrounding electrode members 54B on both sides of the first surroundingelectrode member 54A.

The first electrode 18 includes a single electrode member 56 facingagainst the central electrode member 52 and multiple surroundingelectrode members 54.

The voltage application section 22 supplies the ground potential to thefirst electrode 18 and is configured to be capable of applying thevoltage E selectively to each of the central electrode member 52 and sixsurrounding electrode members 54 of the second electrode 20.

Next, operations of the optical element 10 will be described.

First of all, an operation will be described in a case that the holdingchamber 30 of the optical element 10 changes from the state thatinterrupts light to the state that allows light to pass therethrough.

As shown in FIG. 19, the first liquid 14 is initially positioned betweenthe electrode member 56 of the first electrode 18 and the centralelectrode member 52 of the second electrode 20 in the holding chamber30.

Under this state, the voltage application section 22 applies the voltageE to the central electrode member 52 and opens (or applies the groundpotential to) the remaining six electrode members 54.

Thus, the electric field by the voltage E applied to the first electrode18 and central electrode member 52 acts on the first liquid 14 facingthe central electrode member 52, whereby the first liquid 14 does notmove and can be held at the position. As a result, a most part of thefirst liquid 14 faces the central electrode member 52, and parts of thefirst liquid 14 face the adjacent six surrounding electrode members 54.

Under this condition, the incident light traveling toward the holdingchamber 30 is interrupted by the first liquid positioned in the holdingchamber 30 and having a low transmittance.

Next, as shown in FIG. 20, the voltage application section 22 opens (orapplies the ground potential to) the central electrode member 52 and thefour second surrounding electrode members 54B and applies the voltage Eto the two first surrounding electrode members 54A. In other words, theposition subject to the voltage application to the second electrode 20is changed to the first surrounding electrode members 54A.

Then, the electric field by the voltage E applied to the first electrode18 and the two first surrounding electrode members 54A acts on the firstliquid 14 facing the central electrode member 52, whereby the firstliquid 14 surrounded by the second liquid 16 is divided into two andmoves toward the two first surrounding electrode members 54A.

Thus, the first liquid 14 is divided into two, which are then heldfacing the two first surrounding electrode members 54A.

In this case, most parts of the divided first liquid face the firstsurrounding electrode members 54A, and parts of the divided first liquid14 face the adjacent central electrode member 52 and second surroundingelectrode members 54B.

Next, as shown in FIG. 21, the voltage application section 22 opens (orapplies the ground potential to) the central electrode member 52 and thetwo first surrounding electrode members 54A and applies the voltage E tothe four second surrounding electrode members 54B. In other words, theposition subject to the voltage application to the second electrode 20is changed to the second surrounding electrode members 54B.

Then, the electric field by the voltage E applied to the first electrode18 and four second surrounding electrode members 54B acts on the firstliquid 14 facing the first surrounding electrode members 54A, wherebythe first liquid 14 surrounded by the second liquid 16 is divided intotwo, which then move toward the second surrounding electrode members54B.

Thus, the first liquid 14 is divided into four, which are then heldfacing the four second surrounding electrode members 54B.

In this case, most parts of the divided first liquid 14 face the secondsurrounding electrode members 54B, and parts of the divided firstliquids 14 face the adjacent central electrode member 52 and the firstsurrounding electrode member 54A.

Under this condition, the incident light traveling toward the holdingchamber 30 passes through the second liquid positioned in the holdingchamber 30 and having a high transmittance.

Next, an operation will be described in a case that the holding chamber30 of the optical element 10 changes from the state that allows light topass therethrough to the state that interrupts light, conversely to theabove.

As shown in FIG. 21, the first liquid 14 is divided into four, which arepositioned at the positions facing the four second surrounding electrodemembers 54B. Under this state, the voltage application section 22applies the voltage E to the central electrode member 52 and opens (orapplies the ground potential to) all of the two first surroundingelectrode members 54A and four second surrounding electrode members 54B.

Thus, the electric field by the voltage E applied to the first electrode18 and central electrode member 52 acts on the first liquids 14 facingthe four second surrounding electrode members 54B, whereby the dividedfirst liquids 14 surrounded by the second liquid 16 move to the centralelectrode member 52.

Hence, as shown in FIG. 19, the four divided first liquids 14 arecombined on the central electrode member 52.

Therefore, the electric field by the voltage E applied to the firstelectrode 18 and central electrode member 52 acts on the first liquid14, whereby the first liquid 14 does not move and can be held at theposition facing the central electrode member 52. As a result, a mostpart of the first liquid 14 faces the central electrode member 52, andparts of the first liquid 14 face the adjacent first surroundingelectrode members 54A and second surrounding electrode members 54B.

Under this condition, the incident light traveling toward the holdingchamber 30 is interrupted by the first liquid positioned in the holdingchamber 30 and having a low transmittance.

Like the first embodiment, the optical element 10 according to the sixthembodiment can be functioned as a shutter by switching the holdingchamber 30 between the state that allows light to pass therethrough andthe state that interrupts light by changing the position subject to thevoltage application by the voltage application section 22 and dividingand moving the first liquid 14 between the central electrode member 52and the surrounding electrode members 54.

According to the sixth embodiment in particular, after the first liquid14 is divided into two first, and each of the two divided first liquids14 is divided into two. Therefore, the voltage enough for dividing thefirst liquid 14 into two may be only required to apply to the firstsurrounding electrode members 54A and second surrounding electrodemembers 54B. The voltage may be also smaller than the voltage fordividing the first liquid 14 into four simultaneously, which isadvantageous for reducing power consumption.

In moving the four divided first liquids 14 to the central electrodemember 52 and combining them into one, the speed of the movement of thefirst liquids 14 can be increased since the volume and mass of each ofthe four divided first liquids 14 are smaller than the volume and massof the two divided first liquids 14. This is more advantageous for theimprovement of the response property of the optical element 10.

Having described the cases that the first liquid 14 is divided into two,four and eight by providing two, four and eight electrode members as themultiple electrode members according to the embodiments, the number ofthe multiple electrode members is not limited thereto. Apparently, twoor higher even-numbered or odd-numbered electrode members may beprovided as the multiple electrode members to divide the first liquid14.

Having described the case in which the optical element 10 is functionedas a shutter according to the embodiments, the optical element 10 may beapparently functioned as a Neutral Density Filter (ND filter). In thiscase, the transmittance of one of the first liquid 14 and the secondliquid 16 may be changed to the value for functioning as the ND filter,and the transmittance of the other one of the first liquid 14 and thesecond liquid 16 may be changed to 100%.

Multiple kinds of ND filter having different transmittances (beamattenuation rates) may include the optical elements 10, and the multipleoptical elements 10 may be multi-layered on the optical axis of theimaging apparatus 100 to provide an ND filter that can switch between oramong multiple beam attenuation rates.

Having described the case in which the imaging apparatus 100 is adigital still camera or video camera according to this embodiment, theinvention is widely applicable to various imaging apparatus such as acellular phone with a camera, a Personal Digital Assistant (PDA) with acamera and a notebook PC with a camera.

It should be understood by those skilled in the art that variousmodifications, combinations, sub-combinations and alterations may occurdepending on design requirements and other factors insofar as they arewithin the scope of the appended claims or the equivalents thereof.

1. An optical element comprising: a container having first and secondend walls facing against each other in a direction that light passesthrough and end walls connecting the first and second end walls so as toform a holding chamber therein; a polar or conductive first liquidwithin the holding chamber; a second liquid within the holding chamberand not mixing with the first liquid; a first electrode provided at thefirst end wall; a second electrode having a center electrode member anda pair of electrode members each provided at a position corresponding tothe first electrode in said direction; and voltage application means forapplying voltage between the first electrode and the second electrodefor applying an electric field to the first liquid; wherein the voltageapplication means applies voltage between the first electrode and thepair of electrode members when the first liquid is positionedcorresponding to the center electrode member in said direction so thatthe first liquid is divided and the divided first liquids move atpositions corresponding to each of the pair of electrode members, andapplies voltage between the first electrode and the center electrodemember when each of the divided first liquids are positioned at aposition corresponding to each of the pair of electrode members in saiddirection so that the divided first liquid move to the positioncorresponding to the center electrode member thereby the divided firstliquid is connected as one.
 2. The optical element according to claim 1,wherein transmittance of the first liquid is lower than that of thesecond liquid.
 3. The optical element according to claim 2, wherein theapparatus is used for shutter of an imaging apparatus and the shutter isclosed when the first liquid is positioned corresponding to the centerelectrode member in said direction.
 4. The optical element according toclaim 3, wherein the control of opening of the shutter comprises twosteps.
 5. The optical element according to claim 4, wherein the shutteris open when the first liquid is further divided by next applyingvoltage to additional electrodes adjacent to each of the pair ofelectrode members, the next applying being subsequent to the dividing ofthe first liquid by application of voltage between the first electrodeand the pair of electrode members.
 6. An optical element comprising: acontainer having first and second end walls facing against each other ina direction that light passes through and end walls connecting the firstand second end walls so as to form a holding chamber therein; a polar orconductive first liquid within the holding chamber; a second liquidwithin the holding chamber and not mixing with the first liquid; a firstelectrode provided at the first end wall; a second electrode having acenter electrode member and a pair of electrode members each provided ata position corresponding to the first electrode in said direction; and avoltage source to apply voltage between the first electrode and thesecond electrode to apply an electric field to the first liquid; whereinthe voltage source applies voltage between the first electrode and thepair of electrode members when the first liquid is positionedcorresponding to the center electrode member in said direction so thatthe first liquid is divided and the divided first liquids move atpositions corresponding to each of the pair of electrode members, andapplies voltage between the first electrode and the center electrodemember when each of the divided first liquids are positioned at aposition corresponding to each of the pair of electrode members in saiddirection so that the divided first liquid move to the positioncorresponding to the center electrode member thereby the divided firstliquid is connected as one.
 7. The optical element according to claim 6,wherein transmittance of the first liquid is lower than that of thesecond liquid.
 8. The optical element according to claim 7, wherein theapparatus is a shutter of an imaging apparatus and the shutter is closedwhen the first liquid is positioned corresponding to the centerelectrode member in said direction.
 9. The optical element according toclaim 8, wherein the control of opening of the shutter comprises twosteps.
 10. The optical element according to claim 9, further comprisingadditional electrodes adjacent to each of the pair of electrode members,wherein the shutter is open when the first liquid is further divided bynext applying voltage to the additional electrodes, the next applyingbeing subsequent to the dividing of the first liquid by previouslyapplying of voltage between the first electrode and the pair ofelectrode members.
 11. An optical element comprising: a container havinga first and second end walls facing against each other in a directionthat light passes through and side walls connecting the first and secondend walls so as to form a holding chamber therein; a polar or conductivefirst liquid contained in the holding chamber; a second liquid containedin the holding chamber and not mixing with the first liquid; a firstelectrode provided at the first end wall; a second electrode having acenter electrode member and multiple surrounding electrode membersextending in a direction orthogonal to said direction that light passesthrough; and voltage application means for applying a voltage to thefirst electrode and the second electrode for applying an electric fieldto the first liquid; wherein the voltage application means puts theoptical element in a first light transmission state by applying avoltage to the first electrode and at least two of the multiplesurrounding electrode members when the first liquid is positionedcorresponding to the center electrode member so that the first liquid isdivided and the divided first liquids move in said orthogonal directiontowards positions corresponding to at least two of the multiplesurrounding electrode members, and puts the optical element in a secondlight transmission state by applying a voltage to the first electrodeand the center electrode member when each of the divided first liquidsare positioned at a position corresponding to at least two of themultiple surrounding electrode members so that the divided first liquidsmove towards the position corresponding to the center electrode memberthereby the divided first liquids are connected as one.
 12. The opticalelement according to claim 11, wherein the number of surroundingelectrode members is six such that there are three surrounding electrodemembers on each side of the central electrode member.
 13. The opticalelement according to claim 11, wherein optical transmittance of thefirst liquid is lower than the optical transmittance, of the secondliquid.
 14. The optical element according to claim 11, wherein opticaltransmittance of the second liquid is lower than the opticaltransmittance of the first liquid.
 15. The optical element according toclaim 12, wherein the optical element is a shutter of an imagingapparatus.
 16. The optical element according to claim 12, wherein theshutter is closed when the first liquid is positioned corresponding tothe center electrode member in said direction that light passes through.17. The optical element according to claim 16, wherein two steps controlwhen the shutter opens.
 18. The optical element according to claim 8,wherein a first of said two steps said first liquid is divided into twoand in a second of said two steps each of said two divided first liquidsis further divided such that said first liquid is divided into four.